Low temperature fabrication of molybdenum and alloys thereof



Patented Jan. 26, 1954 UNHTED STATES Mem orrrce LOW TEMPERATURE FABRICATION F MOLYBDENUM AND ALLYS THEREOF Application September 21, 1951, Serial No. 247,652

9 Claims.

This invention relates to molybdenum and, more particularly, to its :fabrication at low temperatures.

The principal object of our invention, generally considered, is to work molybdenum under compressive stress at low temperatures, terminating the treatment with a stress-relieving anneal from a temperature below that of grain growth.

Another object of our invention is to work molybdenum by compression at a slow rate when approximately at room temperature.

A further object of our invention is to work molybdenum under compression at a slow rate of speed, and nally stress relieve it by treatment at about 1200 C., allowing it to cool nearly to room temperature, or to as low as 200 C., for about 24 hours, or at a rate of 60 C. or less per hour.

Other objects and advantages of the invention will become apparent as the description proceeds.

-and sintered metal prior to working.

Fig. 4 is a similar view of the same bar after cold working in accordance with our invention.

Fig. 5 is a perspective View of a cylinder of pressed and sintered'metal prior to working.

Fig. 6 is a similar View of said cylinder after formation of a pocket therein by cold working at a slow speed.

Fig. 'l is a diagram showing how hardness of pressed and sintered molybdenum increases when compressed at room temperature to various degrees.

Molybdenum, prior to being worked, is brittle and, prior to the present invention, there has been no known method of fabricating at room temperature ingots thereof which were merely Sintered after pressing the powder. Tensile tests of such merely heat-treated molybdenum, prior to working such as hot rolling and annealing which would developits strength, show that it as well as alloys thereof containing small percentages of metal such as cobalt, nickel, iron and tungsten, have no appreciable ductility under tension and an ultimate strength of only about 50,000 lbs. per square inch.

By the expression alloys of molybdenum with small proportions of metal selected from thel (Cl. 14S-11.5)

group consisting of cobalt, nickel, iron and tungsten, we mean such in which the proportion of any one of the first three mentioned alloying metals is not greater than 1/2%, and in which the proportion of alloying tungsten is not greater than 20%. l

When a block of such merely pressed and sintered molybdenum powder, for example, is struck a sharp blow while at room temperature, the block shatters. So it is impossible to roll or forge such heat-treated unworked metal at such low temperatures. The experience of workers in the art indicates that rolling, forging, or other working must start at or above 1200 C.

In accordance with our invention, however, we take a piece of unworked molybdenum, or such containing small percentages of another metal as enumerated above, and deform it while cold, that is, at room temperatures which we have defined as those between 15 and 35 C., or merely slightly warmed but still at a relatively cold temperature and one not above 200 C., by compressing at a slow rate of speed. Under such treatment, a cylinder H of pressed and sintered powder, shown in Figure 1, on slow compression deforms to the generally barrel shape l2 of Fig. 2. A bar i3, as shown in Fig. 3, on slow compression deforms to the bulged shape I4 of Fig. 4. in pressing a pocket in a shape l5, shown in Fig. 5, by slow action on an article of pressed and sintered molybdenum powder, we get a lshape I6 such as shown in Fig. 6.

In effecting such compression, a selected piece of molybdenum is placed between hardened steel platens in a hydraulic press and slowly but uniformly compressed. The press preferably closes at a rate of' about l or less per minute to decrease the height of the sample a desired amount, or otherwise deform it, for example, as shown in Fig. 6. After such compression, which may warm the article slightly due to the conversion of work into heat, the article is placed in a furnace at a desired stress-relieving temperature below that of grain growth such as, for example, about 1200 C. The power to the furnace is then cut oli and the sample allowed to cool nearly to room temperature at a rate of cooling, for example, such as described in the cfa-pending application of Baker and Byron, Serial No. 246,654, led September 14, 1951, Ductilizing Molybdenum and Alloys Thereof, and owned by the asignee of the present application or; for example, the furnace may be cooled nearly to room temperature, or as low as 200 C. in about 24 hours or at the rate of C. or less per hour.

The pressure required for deforming pieces of molybdenum is shown by the curve il in Fig. 7. From this it appears that to decrease the height about 6% takes approximately '75,000 lbs. per

lization. We have also discovered that extremely high density, indicating well-treated material, is not required in starting the process. Also, it makes little diii'erence in the working schedule,

powder, at temperatures below that of recrystalsquare inch. However, as the piece is corn- 5 in accordance with our invention, Whether pure pressed, it works strains so that to compress it molybdenum or such allyed with cobalt, for as much as 50% in height, a pressure of about example, in the amount of 1%, .2% or 3%, is 150,000 lbs. per square inch is required. Of used. course, the pressure required decreases as the The rstrength and elongation Values of Table working temperature is increased and vice versa. II are those where the tensile specimens were Many samples in several sizes have been cold cut across the sample, that is, at right angles worked in this fashion and the following table to the direction of pressing or in the direction is merely an example to indicate the pressure re in which metal ilow takes place during the cold quired at alUDI'OXmately 25 C. com-pression of our invention. These iigures are Table I l5 comparable to those obtained by cutting tensile c A l specimens from samples along the direction of [Or1g1nal vample. Mo -l- .1% ggkllelntl .750 diam. 625 hardness rol-1mg if hot rolling is resorted to. The ducti ties obtained were found to be far superior to Load Re Pressure Height those obtainable by a similar amount of reducquired, Dfgsr' Siggi@ Rlfugeerd Demme, 20 tion in normal factory practice. The utility and 1b.s sqfinch Percent desirability of our method of obtaining good ductility in special sizes and diameters, will, therefore, be apparent. 1 Although a preferred embodiment of our ing g Vention has been described, it will be understood :ggg ifi; that modicationsmay be made within the spirit .333 .283 .000 140, 500 48.0 and scope of the'invention. 100000.... .353 .021 .005 151,000 53.0 We Claim:

1. The method of manufacturing ductile metal The physical properties obtained on reetangufrom a pressed and sintered article of powdered lar pieces of molybdenum Compressed 33% in particles of the group consisting of molybdenum height iS ndcatedby the following table. and alloys thereof with small proportions of Table II sample' N0 PL1 PLQ PL10 PL11 PL12 PL13 PL14 Pressed side, VPN 201 250 203 205 255 203 Hardness Top, VPN... 171 24s 254 252 208 259 283 Annen-ling Temperaturen o 1,200 1,220 1,215 1,200 1.130 1,100 Time at Temperature,

iuu 2O l0 5 Annealed Hardness,

VPN 150 109 215 221 242 254 Elongation in Percent 0.0 0.2 2.3 22.4 10.3 1.1 0.0 Yield Strength, l03

p. 5.1 50.0 71.7 00.9 71.8 70.8 104.3 108.2 Ultimate Strength, 103

vpsi 50.0 71.7 07.3 04.3 07.3 105.0 108.2

The amount of `work strain is indicated in acmetal of the group consisting of cobalt, nickel, cordance with the above table but the hardness r iron and tungsten, comprising compressing the ofthe original samples, PLl, was about 171 VPN 'm article at room temperature at a rate of speed while after compression the hardness varied from of not more than 1/2 per minute` until deformed v255 1:03265 VPN on the side, and from 2518 to 283 not less than aboutv one-third, heating to a VPN on the top, that is, the surface on which stress-relieving temperature between about l100 pressure was applied. Time, temperature, hard- C. and l220 C., and nally allowing said article ness,- elongation and strength have been rrecorded to cool from that temperature to one not higher after annealing and slow cooling. than 200 C. in a length of time not shorter than Thus, `we have discovered that working molyb- 24 hours. v Y denum and its alloys enumerated may be accom- 2. The method of manufacturing ductile metal plished by cold compression, followed by annealfrom a merely Dressed and sintered article 0f ing, so that hardness, strength and ductility may G0 powdered particles of the group consisting of be obtainedwithout the use of hot rolling or molybdenum vand alloys thereof with small proforging While it is old in the art to cold work portions of metal ofthe group consisting of coordinary common, soft, ductile metal copper balt, nickel, iron and tungsten, comprising comand iron, these show ductilitj/ under tension at pressing said Yarticle within the range of temroom temperature. However, refractory metals perature between about 15 and 35 C. at a rate such as molybdenum, which show no appreciable of speed of--not more than Vg per minute until ductility in tensile tests, have heretofore needed deformed not less than about one-third, heating to be worked at elevated temperatures. to a stress-relieving temperature above about We have, therefore, discovered an entirely new 1100D C. and below that of grain growth, and method for fabricating molybdenum and alloys finally allowing said article to cool slowly to a thereof which has never heretofore been known temperature not higher than 200 C. in a length or resorted to for such metals. In accordance of time not shorter than 24 hours. with our invention, such may now be worked from 3. The method of manufacturing ductile metal the start, after merely pressing and sinteringV the from a pressed and' sintered article of powdered particles of the group consisting of molybdenum and alloys thereof with small proportions of metal of the group consisting of cobalt, nickel, iron and tungsten, comprising compressing the article at room temperature at a rate of about 1/2 per minute until deformed to the desired extent but not less than about one-third, heating to a stress-relieving temperature below that of grain growth but above about 1100 C., and finally allowing said article to cool slowly to a temperature not higher than 200 C. in a length of time not shorter than 24 Ihours.

4. The method of manufacturing ductile metal from a pressed and sintered article of powdered particles of the group consisting of molybdenum and alloys thereof with small proportions of metal of the group consisting of cobalt, nickel, iron and tungsten, comprising compressing the article at room temperature at a rate of speed not greater than 1/2 per minute until deformed not less than about one-third, heating to a teinperature of about 1200 C., and finally allowing said article to cool slowly to a temperature not higher than 200 C. in a length of time not shorter than 24 hours.

5. The method of manufacturing ductile metal from a pressed and sintered article of powdered particles of the group consisting of molybdenum and alloys thereof with small proportions of metal of the group consisting of cobalt, nickel, iron and tungsten, comprising compressing the article at room temperature at a rate of speed not greater than 1/2 per minute until deformed not less than about one-third, .heating to a stressrelieving temperature above about 1100 C. and below that of grain growth, and finally allowing said article to cool at a rate not higher than 60 C. per hour to a temperature not higher than about 200 C.

6. The method of manufacturing ductile metal from a pressed and sintered article of powdered particles of the group consisting of molybdenum and alloys thereof with small proportions of metal of the group consisting of cobalt, nickel, iron and tungsten, comprising compressing the article at room temperature at a rate of speed not greater than l" per minute until substantially deformed, heating to a stress-relieving temperature below that of grain growth but higher than 1100 C., and finally allowing said article to slowly cool to a temperature not higher than about 200 C. a length of time not shorter than 24 hours.

"l. The method of manufacturing ductile metal from a pressed and sintered article of powdered particles of the group consisting of molybdenum and alloys thereof With small proportions of metal of the group consisting of cobalt, nickel, iron and tungsten, comprising compressing the article at a temperature between about 15 and 35 C. at a rate of speed not higher than 1/2 per minute until deformed not less than about one-third, heating to and holding at a temperature of between about 1100 C. and 1220 C. for from about 5 to 20 minutes, and finally allowing said article to cool at a rate not higher than about C. per hour to a temperature not higher than about 200 C.

8. The method of manufacturing ductile metal from powdered particles of the group consisting of molybdenum and alloys thereof with small proportions of metal of the group consisting of cobalt, nickel, iron, and tungsten, comprising pressing the powdered material to a desired shape, heating the pressed shape in a protective atmosphere until the particles are sintered into a strong coherent article, pressing the article at room temperature at a rate of speed not greater than 1/2 per minute until substantially deformed, heating to a stress-relieving temperature below that of grain growth but higher than 1100 C., and finally allowing said article to cool slowly to a temperature not higher than 200 C. in a length of time not shorter than 24 hours.

9. The method of manufacturing ductile metal from powdered molybdenum comprising pressing the powdered material to a desired shape, heating the pressed shape in a protective atmosphere until the particles are sintered into a strong coherent article, pressing the article at room temperature at a slow rate of speed of about l per minute until decreased in height at least onethird, heating to a stress-relieving temperature of about 1200 C., and finally allowing said article to cool slowly from that temperature to one not higher than 200 C. in a length of time not shorter than 24 hours.

JOHN W. MARDEN. STUART V. CUTHBERT.

References Cited in the le of this patent Preprint No. 8.9-30, published by the Electrochemical Society, 1946, pages 377-384. 

1. THE METHOD OF MANUFACTURING DUCTILE METAL FROM A PRESSED AND SINTERED ARTICLE OF POWDERED PARTICLES OF THE GROUP CONSISTING OF MOLYBDENUM AND ALLOYS THEREOF WITH SMALL PROPORTIONS OF METAL OF THE GROUP CONSISTING OF COBALT, NICKEL, IRON AND TUNGSTEN, COMPRISING COMPRESSING THE ARTICLE AT ROOM TEMPERATURE AT A RATE OF SPEED OF NOT MORE THAN 1/2" PER MINUTE UNTIL DEFORMED NOT LESS THAN ABOUT ONE-THIRD, HEATING TO A STRESS-RELIEVING TEMPERATURE BETWEEN ABOUT 1100* C. AND 1220* C., AND FINALLY ALLOWING SIAD ARTICLE TO COOL FROM THAT TEMPERATURE TO ONE NOT HIGHER THAN 200* C. IN A LENGTH OF TIME NOT SHORTER THAN 24 HOURS. 